2. Field of the Invention
The present invention relates to an electro-magnetic induction-type conductivity meter for measuring the electric conductivity of a sample liquid wherein electric current is induced to pass through a liquid sample by electro-magnetic induction and detected by a detector coil to measure the conductivity of a sample. More particularly, the invention relates to a compact leak detector for monitoring the performance of the conductivity meter.
2. Description of Related Art
Electro-magnetic induction-type conductivity meters having a transformer portion consisting of a circular excited coil and a detecting coil extending about a passage of a sample liquid have been known. Meter of this configuration have been formed from a plastic resin casing with sample liquid being transported through the casing. Such a meter has usually been provided with a flange and a holder for mounting a detector element at a midway position relative to a pipeline in order to measure the electric conductivity of a liquid, such as a sample liquid flowing through the pipeline.
There have been efforts to make the casing or housing of superior resins with regard to the characteristics of electric installation and corrosion resistance to the sample liquid. Casings have been made of hard vinyl chloride, polypropylene, polyfluorovinylidene, or Teflon (trade name). Problems have occurred, however, in the production of such casings made of resins in that the wall thicknesses can be irregular. The transformer portion that is to interact with the sample liquid usually has a relatively thin wall construction and in a case where this portion is welded to a relatively thick wall portion, a structural strain can be generated. Over the life of the instrument, frequent contact with a sample liquid will occur and the resins can be damaged or cracked, for example, due to the temperature change of the sample liquid, thereby allowing the sample liquid to enter into the inside of the casing. As a result, the coil of the transformer portion can become corroded. Additionally, the measurement can be affected by the egress of liquid into the transformer portion and eventually the coil of the transformer portion will become corroded, and the conductivity meter will become inoperative. The conventional electro-magnetic induction-type conductivity meters have not taken into account an entrance of the sample liquid into a resin case and accordingly, such a malfunction has not been able to be detected until the coil is actually short-circuited.
An additional problem can occur in not only the metallic transformer case housing and the coil will become corroded and the conductivity meter will be damaged, but further this corrosion can then migrate into the sample liquid and can contaminate the liquid. For example, if a corrosive liquid, such as hydrofluoric acid, HF, is being measured, this HF is highly corrosive and will interact with the metallic transformer case housing to become contaminated with metallic ions, such as iron, zinc, chromium, and cobalt. Accordingly, there is still a demand in the prior art to provide an improved electro-magnetic induction-type conductivity meter.